For occlusion of one protein with an another protein, an application of a solution of the protein onto a surface of the crystalline protein may be considered possible method, though in practical, it is extremely difficult to coat the crystalline protein with the solution of the protein without causing any dissolution. Coating for protection of useful proteins such as enzymes has rarely been performed.
Protection of proteins has conventionally known by attainment of a polymer, such as a polysaccharide or polyethylene glycol, covalently bonded to the protein. The method consists of reaction of the protein with the polymer to bind the functional groups in the protein, such as amino and carboxyl groups, under milder reaction conditions, where the binding site cannot be controlled. Therefore the method to protecting the protein cannot be applied to any kind of proteins.
Generally speaking, for preservation purpose of proteins, storage at lower temperatures and adding or mixing of a substance such as a polysaccharide and polyethylene glycol which is expected to stabilize the protein structure are performed. In any method, the protein to be protected will be dissolved together with the substance added and lose its stability when changes occur in the environment, especially when water comes in contact or temperature increases, or in case of dew condensation. Proteins will lose its function when degraded or ingested by microorganisms.
Polymeric proteins such as certain enzymes and antibody completely lose their functions when a part of the molecule is degraded by protease. They lose their functions quickly even when kept frozen due to weaker maintenance of their higer-order configuration.
To investigate the stability of an objective protein protected, it is necessary to isolate the protein and to check its individual function.
AS crystallization of a protein, smaller size crystals are generally obtained in research for the crystallization conditions, for example, by addition of a suitable metallic salt to a concentrated protein solution. There is no rule in crystallization, and therefore a number of crystallization conditions should be examined for each type of proteins to be crystallized.